I had just written a whole bunch and realized...this is going to cost you just a lot of money, no matter what you do.
If you can figure out where the leak is? Eternabond tape. Lots of it. And get it right..you can't just pull it up and do it again. Once down...it likes to stay down.
Get a moisture meter from your local Lowe's or Home Depot. Check to see just where you have wet to where you have dry. If it's in your walls and floor?
If it's just the back wall? You can buy stuff that paints on and stops rot and seems to harden up the existing wood.
http://www.pcepoxy.com/our-products/wood-repair/pc-rot-terminator.phpIf you have done the moisture meter thing and it's walls and floor AND the back wall? Throw it away.
Gary Haupt